This continuation of an established program emphasizes the techniques and concepts of cellular and molecular biology, genetics, and fundamental studies of immunology and bone biology of rheumatic diseases. Original population-based clinical research employs rigorous methodological design and statistical analysis. Support is requested for 6 postdoctoral trainees having either an MD, or PhD, or both, as well as for 1 predoctoral (PhD candidate) trainee. The faculty are carefully selected in areas of: 1) Basic Research in T Cell Biology and Antigen Presentation, B Cell Biology, Mast Cell Biology, Basic Cell Biology, and Bone and Joint Biology. 2) Translational Research in Animal Models and In Vitro Human Studies of Rheumatic Disease and in Genetics and Genomics of Rheumatic Disease. 3) Clinical Research in Population- Epidemiology and Outcomes in Rheumatic Diseases. While the primary strength of the program resides in the direct and individual nature of the interaction in the laboratory between each fellow and the responsible faculty member(s), substantial didactic experiences and the medical school environment supplement training and a series of structures and activities foster interactions. Trainees audit semester courses at Harvard Medical School in their field of basic science, while population science investigators obtain an MPH at the Harvard School of Public Health. Graduate students begin training after completion of course work and are in the Harvard PhD Program in Biomedical and Biological Sciences. The program is based in the Division of Rheumatology, Immunology and Allergy at Brigham and Women's Hospital. Importantly, a significant number of faculty are part of the program but located at other Harvard Medical Institutions who are selected based on their outstanding scientific and training expertise. They include 1) faculty in Genetics and Genomics based at The Broad Institute and the MGHI, 2) faculty in Immunology at The Children's Hospital, the Harvard School of Public Health and the Harvard Department of Pathology, and 3) faculty in Bone and Joint biology based at the Harvard School of Dental Medicine and Children's Hospital. The activities of this program have a major impact on training in musculoskeletal and immunology research.